Processibility and lacing resistance when silanized pigments are incorporated in polymers

ABSTRACT

White-pigmented polymers (particularly, polyolefins such as polyethylene) containing white pigments treated with at least one silane or a mixture of at least one silane and at least one polysiloxane are disclosed to improve processibility in compounding and improve performance properties such as lacing resistance in a polymeric matrix.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/477,754filed on Jun. 7, 1995, now U.S. Pat. No. 5,631,310 which is a divisionalof application Ser. No. 08/203,108 filed Feb. 28, 1994 now U.S. Pat. No.5,607,994.

BACKGROUND OF THE INVENTION

The present invention relates to white-pigmented polymers (particularly,polyolefins such as polyethylene) containing white pigments treated withan organosilicon compound to improve processibility in compounding andimprove performance properties such as lacing resistance in a polyolefinmatrix.

Treatment of TiO₂ pigment with organosilicon compounds to improvedispersibility in a polymer matrix is well known in the art. Forexample, U.S. Pat. Nos. 4,061,503 and 4,151,154 disclose enhanceddispersibility of TiO₂ in paints and plastics. Therein, the TiO₂ issurface treated with a silane possessing at least two hydrolyzablegroups bonded to silicon and an organic group containing a polyalkyleneoxide group.

In addition, U.S. Pat. 4,810,305 discloses a modified hydrophobicpigment or filler containing 0.05 to 10 weight % of anorganopolysiloxane, with improved dispersibility in synthetic resins.

However, deficiencies in the prior art include, but are not limited to,(1) unacceptable processibility, i.e., dispersibility of TiO₂ pigment ina polymeric matrix at slow rates; and (2) lacing, i.e., development ofimperfections in a polyolefin matrix. Lacing occurs as a result ofvolatiles released from the pigment during high temperature polyolefinfabrication processes. Lacing may also be attributable to TiO₂concentrates picking up moisture. A further disadvantage is that higherloadings of TiO₂ pigment in a polymer concentrate result in slowerprocessing rates.

It has been found that the above combined disadvantages of the prior artcan be overcome by the present invention.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a polymeric matrixcomprising polymer and about 0.01 to about 87% by weight silanized TiO₂pigment, based on the weight of the polymeric matrix, wherein thesilanized TiO₂ pigment has a coating of about 0.1 to about 5% by weight,based on the weight of silanized TiO₂ pigment, of an organosiliconcompound selected from at least one silane, or a mixture of at least onesilane and at least one polysiloxane. It has been found that thesilanized pigmentary TiO₂ provides a unique combination of enhancedprocessibility in a polymeric matrix having higher TiO₂ loadings, andimproved end use performance properties such as lacing resistance in apolyolefin matrix at TiO₂ concentrations ranging from about 0.2 to about20% by weight, based on the weight of the polyolefin matrix.

DETAILED DESCRIPTION

The TiO₂ pigments useful in the present invention generally are in therutile or anatase crystalline form. It is commonly made by either achloride process or a sulfate process. TiCl₄ is oxidized to TiO₂particles in the chloride process. Sulfuric acid and ore containingtitanium are dissolved, and the resulting solution goes through a seriesof steps to yield TiO₂, in the sulfate process. Both the sulfate andchloride processes are described in greater detail in "The PigmentHandbook", Vol. 1, 2nd Ed., John Wiley & Sons, N.Y. (1988), theteachings of which are incorporated herein by reference. The optimumaverage particle size can range from about 0.005 to about 1 micron. TheTiO₂ pigments may also contain ingredients added thereto to furtherimprove dispersibility characteristics or other properties such asdurability. Thus, by way of example, but not limited thereto, thepigment may contain additives and/or inorganic oxides, such as aluminum,silicon or tin as well as triethanolamnine, trimethylolpropane,phosphates, etc. "Silanized" TiO₂ is defined herein to refer to TiO₂treated with either at least one silane, or a mixture of at least onesilane and at least one polysiloxane (collectively referred to herein asorganosilicon compounds).

Suitable silanes have the formula:

    R.sub.x Si(R').sub.4-x

wherein

R is a nonhydrolyzable aliphatic, cycloaliphatic or aromatic grouphaving at least 1 to about 20 carbon atoms;

R' is a hydrolyzable group such as an alkoxy, halogen, acetoxy orhydroxy or mixtures thereof; and

    x=1 to 3.

For example, silanes useful in carrying out the invention includeoctyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane,dodecyltriethoxysilane, tridecyltriethoxysilane,tetradecyltriethoxysilane, pentadecyltriethoxysilane,hexadecyltriethoxysilane, heptadecyltriethoxysilane andoctadecyltriethoxysilane. Additional examples of silanes include, R=8-18carbon atoms; R'=chloro, methoxy, hydroxy or mixtures thereof; and x=1to 3. Preferred silanes are R=8-18 carbon atoms; R'=ethoxy; and x=1 to3. The R=8-18 carbon atoms is preferred for enhanced processibility.R'=ethoxy is preferred for ease of handling. Surprisingly, lower chainalkyl silanes resulted in longer processing times. Mixtures of silanesare contemplated equivalents. Weight content of the silane, based ontotal silanized pigmentary TiO₂ is typically about 0.1 to about 5 weight%, preferably about 0.5 to about 1.5 weight %. In excess of 5 weight %may be used but no particular advantage is observed.

In an alternative embodiment, a mixture of at least one silane with atleast one polysiloxane is useful in carrying out the invention. Suitablepolysiloxanes have the formula:

    (R.sub.n SiO.sub.4-n/2)m

wherein

R is organic or inorganic groups;

n=0-3; and

m≧2.

For example, polydimethylsiloxane (PDMS), vinyl phenylmethyl terminateddimethyl siloxanes, divinylmethyl terminated polydimethyl siloxane andthe like are suitable polysiloxanes. PDMS is a preferred polysiloxane.The silane useful in the mixture may be the silane described above withR=1-8 carbon atoms, R'=alkoxy and x=1 preferred. Weight content of thesilane and polysiloxane, based on total silanized pigmentary TiO₂, isabout 0.1 to about 5.0 weight %, preferably from about 1 to 3 weight %.Especially preferred is about 0.5 to 1 weight % silane with R=4 or 8carbon atoms, R'=alkoxy, and x=1; and 1 weight % PDMS. The ratio ofsilane to polysiloxane can be 1 silane:2 polysiloxane up to 2 silane: 1polysiloxane. An especially preferred ratio is 1 silane: 1 polysiloxane.

The silane and polysiloxane are commercially available or can beprepared by processes known in the art such as those described in"Organosilicon Compounds", S. Pawlenko, et al., New York (1980), theteachings of which are incorporated herein by reference. The method ofaddition is not especially critical and the TiO₂ pigment may be treatedwith the silane in a number of ways. For example, the silane additioncan be made neat or prehydrolyzed to a dry pigmentary base, from aslurry, a filtration step, during drying or at a size operation such asa fluid energy mill, e.g., micronizer, or media mill as described ingreater detail in copending application entitled "IMPROVED SLURRYPROCESS FOR PREPARING SILANIZED TiO₂ PIGMENTS, USING A MEDIA MILL", theteachings of which are incorporated herein by reference, or postblending after micronizing. For example, U.S. Pat. No. 3,834,924describes organosilane and pigment dispersion mixed or blended directlyin a suitable solids mixing apparatus. An example of post blending isdescribed in greater detail in U.S. Pat. Nos. 3,915,735 and 4,141,751.The polysiloxane addition can be made in conjunction with the silane orpost addition to the silanized pigment. The silane addition andpolysiloxane addition is described in greater detail below. If water,either a liquid or vapor (steam), is present as a component of theprocess stream, hydrolysis of the hydrolyzable groups of the silane willoccur and the silane coating will bond to the TiO₂ base. Prehydrolyzingthe silane is a preferred step in treating the TiO₂ pigment with thesilane. If the silane is added neat to the TiO₂ base, then moistureadsorbed on the TiO₂ will effect the hydrolysis, but at a lower ratethan if excess moisture is present. Hydrolysis of silanes is describedin greater detail in "Organofunctional Silanes" by Union Carbide (1991),the teachings of which are incorporated herein by reference.

Polymers which are suitable for use in the present invention include, byway of example but not limited thereto, polymers of ethylenicallyunsaturated monomers including olefins such as polyethylene,polypropylene, polybutylene, and copolymers of ethylene with higherolefins such as alpha olefins containing 4 to 10 carbon atoms or vinylacetate, etc,; vinyls such as polyvinyl chloride, polyvinyl esters suchas polyvinyl acetate, polystyrene, acrylic homopolymers and copolymers;phenolics; alkyds; amino resins; epoxy resins, polyamides,polyurethanes; phenoxy resins, polysulfones; polycarbonates; polyetherand chlorinated polyesters; polyethers; acetal resins; polyimides; andpolyoxyethylenes. The polymers according to the present invention alsoinclude various rubbers and/or elastomers either natural or syntheticpolymers based on copolymerization, grafting, or physical blending ofvarious diene monomers with the above-mentioned polymers, all asgenerally known in the art. Thus generally, the present invention isuseful for any such white-pigmented plastic or elastomeric compositions(collectively referred to herein as a white-pigmented polymers). Forexample, but not by way of limitation, the invention is felt to beparticularly useful for polyolefins such as polyethylene, polypropylene,polyvinyl chloride, polyamides and polyesters.

As used herein, "high loaded" TiO₂ may vary widely for each polymericmatrix but will be in a well known range for those skilled in the art.For example, in a polyolefin matrix, a high loaded TiO₂ would be 50 orabove % by weight TiO₂ pigment, based on the weight of the polyolefinmatrix.

A wide variety of conventional additives may be included in the polymersas is necessary, desirable or conventional for the intended end use.Such additives include, but are not limited to, antioxidants, lightstabilizers, lubricants, thermal processing additives and the like.

TiO₂ coated with organosilicon compounds can be incorporated into amelt-fabricable polymer to form the polymer composition of thisinvention by any melt compounding technique known in the art. Generally,TiO₂ and polymer resin are brought together and then mixed in a blendingoperation that applies shear to the polymer melt. The polymer resin isusually available in the form of powder, granules, pellets, or cubes.Commonly, TiO₂ and resin are first combined while the resin is in thesolid state (not melted) and dry-blended in some way. This can be donein simple ways, such as by shaking in a bag or tumbling in a closedcontainer, or in more sophisticated ways such as by using blendershaving agitators or paddles. TiO₂ and polymer resin can be broughttogether by co-feeding the materials to internal mixers and allowing ascrew to mix them together before the resin reaches the molten state.The melt blending of TiO₂ and polymer resin can be done using knownequipment, such as single-screw extruders, twin-screw extruders,internal mixers, and the like. Internal mixers are commonly used. Themelt blending can be done as part of the process of forming a finishedarticle of the composition, as by melt extrusion. Alternatively, themelt blending can be done in a preliminary step, optionally isolatingthe polymer composition, e.g., as cubes, followed by forming a finishedarticle in a subsequent process. As one skilled in the art willrecognize, there are many possible variations of the technique forpreparing polymer compositions of the invention. One may, for example,first prepare a concentrate having high TiO₂ concentration, i.e., onecomposition of the invention, and then combine the concentrate withpolymer resin containing no TiO₂ to obtain another composition of theinvention.

The highly loaded polymer concentrates are made as described above withthe desirable weight % for the intended end use. For example, inpolyolefin concentrates, about 50-87% by weight concentrate may be usedto opacity. The concentrate is "let down" into the polyolefin. Usedherein, "let down" refers to a ratio or percent of resin mixed withconcentrate. Let down may be accomplished in a number of ways and isdescribed in great detail in "Film Extrusion Manual" (1992), theteachings of which are incorporated herein by reference. For example, inlacing evaluation, a 50 wt. % to 87 wt. % concentrate may be let down toabout 0.2 to about 20 weight % by dry mixing polyolefin and extruding ata specific processing temperature and casting it into a film. Pigmentperformance is then evaluated in an end use application.

The highly loaded silanized pigmentary TiO₂ exhibits outstandingprocessibility in a polymeric matrix and lacing resistance whenincorporated into a polyolefin matrix. Additional advantages observedare increased bulk density, lower viscosity, excellent dispersibility,moisture resistance, and excellent optical properties such as high tintstrength.

The following examples are construed as illustrative and not limitativeof the remainder of the disclosure in any way whatsoever. Farrel BRBanbury\-type mixers (available from Farrel Corp., Ansonia, Conn., USA)have been used in the Examples. Broad range internal mixers as known inthe art are contemplated equivalents. For example, Farrel ContinuousMixers (FCM) (available from Farrel Corp., Ansonia, Conn., USA) and twinscrew extruders are equally applicable.

Bulk density is given as grams per cubic centimeter of uncompactedpigment. A pigment bulk density below about 0.6 will result in difficultsolids handling in polymer compounding. For rapid compounding of TiO₂and a polymer in a Banbury\-type mixer, a bulk density above about 0.6is desirable.

Total flux time is a measure of processing time, or time to disperse, ina Banbury\-type mixer.

Viscosity, at 180 degrees Celsius, of product from the Banbury\-typemixer, was measured at a shear rate of 550 1/sec. Viscosity was measuredwith a Kayeness capillary rheometer (available from Kayeness Corp.,Honey Brook, Pa., USA).

EXAMPLES PREPARATION OF A CONCENTRATE, i.e., MASTERBATCH

In the following examples, a 70 wt. % compound of a dry mix TiO₂ balancepolyethylene was prepared in the following manner. First, a dry mix ofTiO₂ /balance polyethylene was prepared via blending of 1562 grams ofthe TiO₂ with 670 grams of polyethylene. The polyethylene used for theexperiments was a low density polyethylene supplied by Quantum U.S.I.Chemicals--Code=NA212 (Cincinnati, Ohio, USA).

The dry mix of TiO₂ /polyethylene was added to the feed hopper of alaboratory Farrel BR Banbury\-type Mixer (chamber capacity=about1100-about 1200 cc). The dry mix was then discharged into the Mixer.Stock pressure equaled 56 psi, driven rotor speed=230 rpm, coolingwater=85° F. The Mixer was equipped with recording equipment for batchtemperature, power consumption, ram pressure, and heat loss.

The mixture of TiO₂ /polyethylene was subsequently processed until theTiO₂ dispersed into the melted resin (temperature=for example 220° F.)defined above as total flux time. The compound was then discharged fromthe mixer.

EXAMPLE 1

3000 grams of neutralized pigmentary rutile TiO₂ were weighed into a panand sprayed with 30 grams of butyl trimethoxy silane, as supplied byUnion Carbide now Osi Specialty, Inc. (Tarrytown, N.Y., USA).

The treated pigment was ground in a fluid energy mill, e.g., micronizerwith superheated steam.

The micronized pigment was mixed in a Patterson-Kelley V-Blender with 30grams of polydimethylsiloxane, as supplied by Petrach now Huls Corp.(Piscataway, N.J., USA).

The treated TiO₂ polyethylene concentrate was prepared as describedabove.

EXAMPLE 2

Same as Example 1 except that octyl triethoxy silane was used in placeof butyl trimethoxy silane.

EXAMPLE 3

Neutralized pigmentary rutile TiO₂ was treated with about 1 wt % of eachof octyl triethoxy silane and polydimethylsiloxane as for Example 1,except that these compounds were added at the micronizer, throughexisting nozzles in a grinding chamber. The treated pigment and lowdensity polyethylene were then mixed and processed in a Banbury\-typemixer to form a 70 wt % masterbatch, as described above.

EXAMPLE 4

Neutralized pigmentary rutile TiO₂ was treated with about 1 wt % ofoctyl triethoxy silane, by spraying, as for Example 1. There was notreatment with polydimethylsiloxane. The treated pigment was micronized,and used for processing in a Banbury\-type mixer to a 70 wt %polyethylene masterbatch, as described above.

COMPARATIVE EXAMPLE 5 (C-5)

Pigmentary rutile TiO₂ and low density polyethylene were mixed andprocessed in a Banbury\-type mixer to form a 70 wt % polyethylenemasterbatch, as described above.

The results of the tests on the masterbatches from Examples 1-5 aresummarized in the table below.

    ______________________________________              Bulk         Total              Density      Flux   Viscosity    Example   g/cc)        (s)    (p)    ______________________________________    1         0.96         26     3675    2         1.01         26.2   3681    3         0.78         24.5   3479    4         0.97         28.2   3927    C-5       0.54         37.6   4459    ______________________________________

This data demonstrated the processing advantages of organosiliconcompound treated pigments (Examples 1-4) versus a non-treated pigment(Example C-5) in a 70 wt. % TiO₂ /polyethylene masterbatch. Shown in thetable are bulk density improvements realized by the organosiliconcompound treatments, total flux time improvements, and viscosityimprovements for these materials over non-treated.

EXAMPLE 6

Dried, crushed, meshed pigmentary rutile TiO₂ filter cake was sprayedwith about 1 wt. % of neat octyl triethoxy silane, as supplied by Osi.

The treated pigment was micronized and used for processing in aBanbury\-type mixer to a 70 wt. % polyethylene masterbatch, as describedabove.

COMPARATIVE EXAMPLE 6A

Same as Example 6 except butyl trimethoxy silane was used in place ofoctyltriethoxysilane. The results of the tests on the masterbatches fromExamples 6-6A are summarized in the table below.

    ______________________________________              Bulk         Total              Density      Flux   Viscosity    Example   g/cc)        (s)    (p)    ______________________________________    6         0.97         28     3927    6A        0.77         48     3921    ______________________________________

This data demonstrated the differences for a higher chain alkyl silane(Example 6) versus a lower chain alkyl silane. Surprisingly, the lowerchain alkyl silanes resulted in longer processing times. The lower chainalkyl silane realized a 70% increase in processing time over the higherchain alkyl silane.

EXAMPLE 7

3000 grams of pigmentary rutile TiO₂ was treated with 1 weight % (30grams) octyltriethoxysilane via spraying. Material was processed in aBanbury\-type mixer at 70 weight % in a polyethylene masterbatch asdescribed above.

COMPARATIVE EXAMPLE 7A

3000 grams of pigmentary rutile TiO₂ was treated with 1 weight % (30grams) polydimethylsiloxane (PDMS) via spraying. Material was processedin a Banbury\-type mixer at 70 weight % in a polyethylene masterbatch asdescribed above.

EXAMPLE 8

Pigmentary rutile TiO₂ was treated with 1 weight % octadecyltriethoxysilane (available from IHuls) via spraying. Material was processed in aBanbury\-type mixer at 70 weight % in a polyethylene masterbatch asdescribed above.

The results of tests on the masterbatches from Examples 7, 7A and 8 aresummarized in the table below.

    ______________________________________              Bulk         Total              Density      Flux   Viscosity    Example   g/cc)        (s)    (p)    ______________________________________    7         0.63         30.2   2968    7A        0.59         35.3   3491    8         0.58         33     2746    ______________________________________

This data demonstrated a series of post-blended higher chain alkylsilane (Examples 7 and 8) and siloxane (Comparative Example 7A) treatedmaterials. For the two silane treated materials (Examples 7 and 8)treated with a higher chain alkyl silane, final product viscosities werenearly identical. For the siloxane only (Comparative Example 7A) treatedmaterial viscosity and processing time were higher.

EXAMPLE 9

Silanized pigment, octyltriethoxysilane, and polyester were dry blendedin a double cone blender for 5 minutes to yield a 50/50 mixture. Thismixture was added to a feed hopper of a Farrel Continuous Mixer (FCM).The mixture of treated TiO₂ /polyester was subsequently processed untilthe treated TiO₂ dispersed into the melted resin (temperature=550° F.).Observable flow of the concentrate was smooth and continuous.

COMPARATIVE EXAMPLE 9A

An untreated anatase pigment, Kronos 1072 (available from Kronos,Leverkuesen, Germany), was dry blended, fed and processed in the FCM asin Example 9. Observable flow of the concentrate was not smooth.Continuous flow was not attained.

LACING

Lacing occurs as a function of pigment volatility at specific wt %pigment loadings and processing temperature. For polyethylene filmspigmented with titanium dioxide, 20 wt % TiO₂ in the film processed attemperatures of 620° F. or greater will discern readily lacibility ofthe film. Typically, materials are rated 10 if they do not lace, andbelow 10 if they begin to lace.

Two materials are compared in the following for lacing.

EXAMPLE 10

By weight, 20% of an octyltriethoxy silane treated TiO₂ was compoundedinto balance polyethylene. Material was extruded on a Killion singlescrew extruder through a film die at 620° F. Evaluation of the film on alight box revealed superior integrity with no thin spots or pin-holes.Rating of material equaled 10. Lacing resistance was comparable to theindustry standard, Ti-Pure\R-101, available from E. I. du Pont deNemours and Company, Wilmington, Del., USA.

COMPARATIVE EXAMPLE 10A

By weight, 20% of a siloxane treated pigment RCL-69, (available fromSCM, Baltimore, Md., USA) was compounded into balance polyethylene.Material was extruded on a Killion single screw extruder through a filmdie at 620° F. Material exhibited thin spots under a light box. Materialwas rated as a 7.

Having thus described and exemplified the invention with a certaindegree of particularity, it should be appreciated that the followingclaims are not to be so limited but are to be afforded a scopeconmmensurate with the wording of each element of the claim andequivalents thereof.

What is claimed is:
 1. A process for silanizing TiO₂ pigment and forhighly loading the silanized TiO₂ pigment in a polymer concentrate,comprising the steps of:(a) adding a silane compound to a slurrycomprising TiO₂ pigment and water, the silane compound having theformula:

    R.sub.x Si(R').sub.4-x

wherein, R is a nonhydrolyzable aliphatic, cycloaliphatic or aromaticgroup having 8-20 carbon atoms; R' is a hydrolyzable group selected fromalkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and

    x=1 to 3;

to form silanized TiO₂ pigment; and (b) mixing the silanized TiO₂pigment with a polymer resin to form a highly loaded polymer concentratecomprising about 50 to about 87% by weight silanized TiO₂ pigment.
 2. Aprocess for silanizing TiO₂ pigment and for highly loading the silanizedTiO₂ pigment in a polymer concentrate, comprising the steps of:(a)silanizing TiO₂ pigment in a slurry comprising TiO₂ pigment and water bytreating TiO₂ pigment with a mixture of a silane compound and apolysiloxane compound, the silane compound having the formula:

    R.sub.x Si(R').sub.4-x

wherein, R is a nonhydrolyzable aliphatic, cycloaliphatic or aromaticgroup having 1-20 carbon atoms; R' is a hydrolyzable group selected fromalkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and

    x=1 to 3;

and (b) mixing the silanized TiO₂ pigment with a polymer resin to form ahighly loaded polymer concentrate comprising about 50 to about 87% byweight silanized TiO₂ pigment.
 3. The process of claim 2, wherein thepolysiloxane compound has the formula:

    (R.sub.n SiO.sub.4-n/2).sub.m

wherein, R is an organic or inorganic group; n=0-3; and m≧2.
 4. Theprocess of claim 1 or 2, wherein the highly loaded polymer concentratecomprises about 70 to about 87% by weight silanized TiO₂ pigment.
 5. Theprocess of claim 4, wherein the polymer resin is polyethylene.
 6. Theprocess of claim 1 or 2, wherein the silane compound isoctyltriethoxysilane.
 7. The process of claim 1 or 2, wherein the silanecompound is octyltrichlorosilane.
 8. The process of claim 1 or 2,wherein R is an aliphatic having 8-18 carbons, R' is methoxy, ethoxy,chloro, hydroxy, or mixtures thereof, and x=1 to
 3. 9. The process ofclaim 8, wherein R is an aliphatic having 8 carbons, R' is ethoxy,hydroxy, or mixtures thereof, and x=1 to
 3. 10. The process of claim 8,wherein R is an aliphatic having 8 carbons, R' is chloro, hydroxy, ormixtures thereof, and x=1 to
 3. 11. The process of claim 2, wherein R isan aliphatic having 1-8 carbons, R' is methoxy, ethoxy, chloro, hydroxy,or mixtures thereof, and x=1 to
 3. 12. The process of claim 11, whereinR is an aliphatic having 1-8 carbons, R' is ethoxy, hydroxy, or mixturesthereof, and x=1 to
 3. 13. The process of claim 11, wherein R is analiphatic having 1-8 carbons, R' is chloro, hydroxy, or mixturesthereof, and x=1 to
 3. 14. The process of claim 13, wherein R is analiphatic having 6-8 carbons, R' is chloro, hydroxy, or mixturesthereof, and x=1 to
 3. 15. The process of claim 2 or 3, wherein thepolysiloxane is selected from the group consisting ofpolydimethylsiloxane, vinyl phenylmethyl terminated dimethyl siloxane,divinylmethyl terminated polydimethyl siloxane, and mixtures thereof.16. The process of claim 1 or 2, wherein the polymer resin is selectedfrom the group consisting of polyolefins, polyesters, polyvinylchlorides and polystyrenes.
 17. The process of claim 16, wherein thepolyolefin is selected from the group consisting of polyethylene,polypropylene, and polybutylene.
 18. The process of claim 17, whereinthe polyolefin is polyethylene.
 19. The process of claim 1 or 2, whereinthe TiO₂ pigment is silanized with about 0.1 to about 5.0% by weight ofthe silane compound based on the weight of silanized TiO₂ pigment.
 20. Aprocess for silanizing TiO₂ pigment and for highly loading the silanizedTiO₂ pigment in a polymer concentrate, comprising the steps of:(a)treating TiO₂ pigment with a silane compound having the formula:

    R.sub.x Si(R').sub.4-x

wherein, R is a nonhydrolyzable aliphatic, cycloaliphatic or aromaticgroup having 8-20 carbon atoms; R' is a hydrolyzable group selected fromalkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and x=1 to 3toform silanized TiO₂ pigment; and (b) mixing the silanized TiO₂ pigmentwith a polymer resin to form a highly loaded polymer concentratecomprising about 50 to about 87% by weight silanized TiO₂ pigment.
 21. Aprocess for silanizing TiO₂ pigment and for highly loading the silanizedTiO₂ pigment in a polymer concentrate, comprising the steps of:(a)drying TiO₂ pigment and adding to the pigment during drying a silanecompound having the formula:

    R.sub.x Si(R').sub.4-x

wherein, R is a nonhydrolyzable aliphatic, cycloaliphatic or aromaticgroup having 8-20 carbon atoms; R' is a hydrolyzable group selected fromalkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and

    x=1 to 3;

to form silanized TiO₂ pigment; and (b) mixing the silanized TiO₂pigment with a polymer resin to form a highly loaded polymer concentratecomprising about 50 to about 87% by weight silanized TiO₂ pigment.
 22. Aprocess for silanizing TiO₂ pigment and for highly loading the silanizedTiO₂ pigment in a polymer concentrate, comprising the steps of:(a)mixing a silane compound with water, the silane compound having theformula:

    R.sub.x Si(R').sub.4-x

wherein, R is a nonhydrolyzable aliphatic, cycloaliphatic or aromaticgroup having 8-20 carbon atoms; R' is a hydrolyzable group selected fromalkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and

    x=1 to 3;

(b) treating TiO₂ pigment with one or more compounds resulting frommixing the silane compound and water in step (a) to form silanized TiO₂pigment; and (c) mixing the silanized TiO₂ pigment with a polymer resinto form a highly loaded polymer concentrate comprising about 50 to about87% by weight silanized TiO₂ pigment.
 23. A process for silanizing TiO₂pigment and for highly loading the silanized TiO₂ pigment in a polymerconcentrate, comprising the steps of:(a) treating TiO₂ pigment with thereaction products or water and a silane compound having the formula:

    R.sub.x Si(R').sub.4-x

wherein, R is a nonhydrolyzable aliphatic, cycloaliphatic or aromaticgroup having 8-20 carbon atoms; R' is a hydrolyzable group selected fromalkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and

    x=1 to 3

to form silanized TiO₂ pigment; and (b) mixing the silanized TiO₂pigment with a polymer resin to form a highly loaded polymer concentratecomprising about 50 to about 87% by weight silanized TiO₂ pigment.